Bonded non-woven fibrous materials

ABSTRACT

A BONDED FIBROUS MATERIAL CONTAINNG CRIMPED FIBRES IS MADE BY FORMING A FIBROUS STRUCTURE CONTAINING COMPOSITE POTENTIALLY CRIMPABLE FIBRES WHICH COMPRISE TWO FIBREFORMING COMPONENTS ONE OF WHICH IS POTENTIALLY ADHESIVE AND SUBSEQUENTLY DEVELOPING THE CRIMP AND RENDERING THE POTENTIALLY ADHESIVE COMPONENT ADHESIVE.

July 27, 1971 5, D s EI'AL 3,595,731

BONDED Non-WOVEN FIBROUS MATERIALS Filed Aug. 13, 1968 :s Sheets-Sheet 1 azqw mm A Hurnvy 1 g, DAWES ETAL 3,595,131

BONDED NON-WOVEN FIBROUS MATERIALS Filed Aug. 13, 1968 3 Sheets-Sheet 3 July 27, 1971 DAVIES EI'AL 3,595,731

BONDED NON-WOVEN FIBROUS MATERIALS Filed Aug. 15, 1968 3 Sheets-5heet 3 A Hurnvy 5 United States Patent US. Cl. 161l50 22 Claims ABSTRACT OF THE DISCLOSURE A bonded fibrous material containing crimped fibres is made by forming a fibrous structure containing composite potentially crimpable fibres which comprise two fibreforming components one of which is potentially adhesive and subsequently developing the crimp and rendering the potentially adhesive component adhesive.

This is a continuation-in-part of application Ser. No. 342,300, filed Feb. 3, 1964, and of application Ser. No. 342,241, filed Feb. 3, 1964.

This invention relates to bonded fibrous materials containing crimped fibres and more particularly to fibrous materials which are bonded together by the adhesive gllijaracteristics of at least a proportion of their constituent res.

It has already been proposed to manufacture non-Woven fibrous materials by incorporating, in the materials, fibres possessing the ability to crimp, twist or curl and subsequently causing the fibres to crimp, twist or curl by a suitable treatment such that they interlock and mechanically bond the material. Such materials have advantages in terms of drape and handle over materials containing straight fibres and adhesively bonded materials but they are not sufiiciently Well bonded for many end uses and it has in many cases proved necessary to further adhesively bond the materials.

It has been proposed to adhesively bond non-woven materials containing crimped fibres by using homogeneous binder fibres which in some cases have been the crimped fibres themselves and such adhesive bonding has been of two types. One type has been that in which the homogeneous binder fibres have merely been rendered tacky to produce spot welds. Such spot welds do not impair the drape and handle of the materials to any great extent but We have found that they do not add greatly to the strength of the materials. The other type has been that in which the homogeneous binder fibres have been subjected to a more severe treatment to produce materials having the required strength but we have found that such treatment necessarily is such that the homogeneous binder fibres lose their fibrous form and the adhesive spreads through the material. This spread of adhesive produces materials which are much stiller and harsher in handle than the non-adhesively bonded materials, the beneficial effects of the crimped fibres being counteracted by the spread of adhesive.

It has also been proposed to adhesively bond fibrous materials by incorporating in the materials fibres having a coating of a non-fibre-forming resin which resin is subsequently rendered adhesive. Such non-fibre-forming coatings however also spread through the structure on being rendered adhesive under conditions such as to produce materials having the required strength and the materials suffer from the same disadvantages as those bonded with homogeneous binder fibres.

It is an object of the present invention to provide bonded fibrous materials containing crimped fibres which are bonded both mechanically by interlocking of the crimped fibres and adhesively so as to have adequate strength and which are less still and more attractive to handle than prior art adhesively bonded fabrics, the adhesive bonding not detracting from the beneficial effect conferred by the presence of the crimped fibres.

We have found that this object is achieved if particular composite fibres are used to provide both the mechanical and the adhesive bonding by developing latent crimping and adhesive properties. Potentially crimpable composite fibres containing two or more fibre-forming synthetic polymeric components extending continuously along the lengths of the fibres and occupying distinct zones in the cross section of the fibres are known and have been used in fibrous structures. We have now found that if the components of the crimpable composite fibres are chosen so that at least one but not all of the components is potentially adhesive, that is can be rendered adhesive by a treatment which leaves the remainder of each fibre substantially unaffected, the component occupying at least a proportion of the peripheral surface of each fibre, and such fibres are used to form fibrous structures which are mechanically bonded by interlocking of crimped fibres and adhesively bonded, then the potentially adhesive components do not lose their fibrous form on being rendered adhesive under conditions such as to produce an adequately bonded structure. The potentially adhesive components remain associated with the remainder of each fibre thus producing a structure in which adhesive bonding is confined to small areas where the fibres are in contiguous relationship and, since there is no spread of adhesive, the presence of adhesive bonding does not detract from the beneficial effects produced by the crimped fibres and the bonded structures are more drapeable and attractive to handle than the prior art fabrics.

Thus according to the present invention, in one of its aspects, there is provided a bonded fibrous material comprising at least five percent, based on the weight of fibres in the material, of crimped composite fibres comprising at least two fibre-forming synthetic polymeric components arranged in distinct zones across the cross-section of each fibre, each component being continuous along the length of each fibre and at least one, but less than all, of the components being potentially adhesive and located so as to form at least a portion of the peripheral surface of each fibre, said crimp being derived from diiferent physical properties of the components, the fibres of the material being entangled with each other due to said crimp and being bonded to each other where they are in contiguous relationship by the adhesive characteristics of said potentially adhesive component whereby the material is strengthened and stabilised.

According to the present invention, in another of its aspects, there is provided a process for making bonded fibrous materials which comprises forming a fibrous structure containing at least five percent, based on the weight of fibres in the assembly, of composite fibres comprising at least two fibre-forming synthetic polymeric components arranged in distinct zones across the cross-section of each fibre, each component being continuous along the length of each fibre and at least one, but less than all, of the components being potentially adhesive and located so as to form at least a portion of the peripheral surface of each fibre, said composite fibres possessing latent crimp due to different physical properties of the components, developing crimp in said fibres in the absence of any appreciable pressure to entangle them with each other, rendering the potentially adhesive component adhesive and bonding the fibres to each other where they are in contiguous relationship by the adhesive characteristics of said component.

By the expression potentially adhesive component we mean a component the adhesive characteristics of which can be developed without substantially afiecting any other component of the composite fibre. For convenience the following discussions will refer to two component composite fibres although it is to be understood that such fibres may, if desired, have more than two components. As used herein the word fibre includes continuous filaments and staple fibres including flock.

The particular components used for the composite fibres used in the present invention can be chosen from a wide range of fibre-forming polymers. Their disposition in fibres can be varied widely, the only limitation being that the components must be chosen and arranged in the fibres so as to provide the fibres with potential crimp and so that one component is potentially adhesive and arranged to occupy at least a portion of the peripheral surface of each composite fibre.

The components may, for example, bear a side-by-side relationship or one component may be completely and eccentrically surrounded by another component, i.e. a form of the so-called sheath and core relationship with the component forming the sheath being the potentially adhesive component, or the composite fibres may be noncircular, for example, trilobal with one or two of the lobes being formed by a potentially adhesive component. The relative proportions of the two components in the composite fibres may be varied in accordance with the end use for which the product is intended.

Suitable components for producing the composite fibres can be found in all groups of synthetic fibre-forming materials. Because of their commercial availability, ease of processing and excellent properties, the condensation polymers, for example, polyamides, and polyesters, and particularly those which can be melt spun are very suitable for use in the present invention. Other composite fibres which may be used include, for example, those based on or containing polyesteramides, polysulphonamides, polyesters, polyolefins, polyurethanes or any combination of these polymers, the only substantial limitation being that the components of the composite fibres should be sufiiciently compatible to resist undue fibrillation.

Examples of suitable composite fibres include those listed in the following table:

Potentially adhesive component Polyhexamethylene Poly (omega-aminoundeeanoic acid). adipamide.

Polyethylene Polypropylene. Polyhexarnethylene A suitable polyurethane.

adipamide.

Polyethyleneterephthalate A polyether-polyurethane copolymer.

A number of methods are available by which the composite fibres may be prepared. Thus, for example, they may be prepared by the methods described in British Pats. Nos.: 579,081; 580,764; and 580,941 which involve co-spinning by a process of melt, plasticised melt, wet or dry spinning, the polymer materials so that they form a unitary filament. Suitable processes and apparatuses for use in the production of composite fibres in which the components are in a side-by-side relationship by melt spinning, are, for example, described in British Pat. Nos. 953,379 and 1,035,908. Prior to or during the spinning operation there may be added pigments, plasticisers, dyes, moth-proofing agents, fire-proofing agents, fillers, abrasives and/or light stabilisers. In particular it may be desirable to add to the spinning solution or otherwise incorporate into the potentially adhesive component of the composite fibres suitable substances for lowering the softening point of that component, such, for example, as plasticisers, soft resins and the like. Among suitable plasticisers for this purpose are dibutyl tartrate, ethyl phthalate, and ethyl glycollate. Examples of suitable soft resins are polyvinyl acetate, ester gum, comarone resin and the lower molecular weight alkyl resins.

The crimp may be developed and the potentially adhesive component activated in one and the same treatment but it is not necessary that the crimping and activation steps be carried out simultaneously and/ or in the same treatment.

The crimp may be developed by subjecting the fibrous material to a heat treatment involving heating the material by various means, as by the application of hot water, oil, steam, air, other fluids which are relatively inert towards the particular composite filament present in the material. The only limitation to the process for develop ing crimp is that there should be no appreciable pressure applied during the process which would prevent the fibres from crimping.

Alternatively, or in addition, crimp development may be effected by subjecting the fibrous material containing the composite fibres to a suitable chemical treatment. Mild acid and alkali baths are examples of what may often be acceptable chemical treatments. Whether crimp be developed by a physical or chemical treatment or by a combination of the two 'we generally find it convenient to activate the potentially adhesive component, thereby bonding together fibres of the material where they are in contiguous relationship, in the same treatment. Thus, crimp and activation may be accomplished by subjecting the fibrous web to a heat treatment in which the temperature exceeds the softening point of the potentially adhesive component. Examples of composite fibres which can be crimped and activated in this manner and the conditions under which these steps can occur are shown in the table below:

adipamide. polyepsilon-eaprolactam.

When the potentially adhesive component of the composite fibres is such that it can be chemically activated the crimping and activation steps may be accomplished in the same chemical treatment. Such a chemical treatment may conveniently be adopted for composite fibres consisting, for example, of various proportions by Weight (for example equal quantities) of polyhexamethylene adipamide as one component and a random copolymer (for example an :20 copolymer) of polyhexamethylene adipamide/poly-epsilon-caprolactam as the other component, in which the two components are arranged in a side-by-side relationship. Such composite fibres can be crimped and the copolymer component rendered adhesive by treating the fibrous material containing the composite-fibres at room temperature in a bath of nitric acid of a suitable strength. In an alternative method such composite fibres can be crimped and activated by exposing the fibrous material to a hot (100 C.) essentially non-aqueous, for example, ethylene glycol, solution of formaldehyde, under conditions which leave the polyhexamethylene adipamide component of the composite fibres substantially non-adhesive.

After activation, the chemical media employed for activating the potentially adhesive component is removed by any suitable means such, for example, as evaporation or washing with a liquid miscible with the aforementioned chemical media but inert towards fibres of the bonded material.

In all circumstances in which crimping and activation are achieved in separate treatments, the fibrous material after crimp has been developed in fibres therein, is subjected to a further treatment to activate the potentially adhesive component thereby bonding together fibres of the web where'they are in contiguous relationship. Bonding in this manner can be accomplished in a variety of ways and in any particular instance the method used is to a large extent dependent on the nature of the potentially adhesive component and also that of the other component of the composite filament. Where the potentially adhesive component has a lower softening point than the other it may conveniently be made adhesive by subjecting the web to a heat treatment which may, for example, be achieved, by the application of dry heat, as by passing hot air through the web or by heating it in an electric oven, or by treating the Web, with moist heat as by the use of moist air, hot water or steam. Other possible methods of heat activation include exposing the web to radiation, for example, infrared radiation of a suitable intensity and duration. When the potentially adhesive component is capable of being activated chemically, activation may be achieved by an appropriate chemical treatment.

It is only necessary that the fibrous structure and the bonded textile material derived therefrom comprise five percent of composite fibres containing a potentially adhesive component, although we prefer such fibres to be present in an amount of percent or more, and other fibres which are not themselves rendered adhesive by the treatment to which the fibrous structure is subjected to develop crimp and/ or to render adhesive the potentially adhesive component may be employed as a blend with such composite fibres. Depending upon the particular desiderata in the bonded textile material to be produced, the percentage of composite fibres containing a potentially adhesive component present in the fibrous structure may be varied widely.

The composite fibres, either in the form of continuous filaments or staple fibres including fiock, may be associated with other fibres or continuous filaments of almost any sort, the only substantial limitation being that those other fibres must not themselves be rendered adhesive by any treatment applied to develop crimp and/or to render adhesive the potentially adhesive components. Wool, silk, flax, cotton, regenerated cellulose, mineral fibres including asbestos and sack wool, glass fibres, synthetic polymeric fibres, other composite fibres and the like are examples of such fibres which may in a particular instance be suitable. For the purposes of this specification and appended claims such fibres are termed non-activatable fibres.

Although, as stated hereinbefore, there should be no appreciable pressure applied to the materials whilst crimp is being developed pressure may be applied after development of crimp but Whilst the potentially adhesive component is adhesive and useful structures can be formed by such application of pressure. Therefore according to the present invention, in another of its aspects, there is provided a process for making bonded fibrous materials which comprises forming a fibrous structure containing at least five percent, based on the weight of fibres in the assembly, of composite fibres comprising at least two fibre-forming synthetic polymeric components arranged in distinct zones across the cross-section of each fibre, each component being continuous along the length of each fibre and at least one, but less than all, of the components being potentially adhesive and located so as to form at least a portion of the peripheral surface of each fibre, said composite fibres possessing latent crimp due to different physical properties of the components, developing crimp in said fibres in the absence of any appreciable pressure to entangle them with each other, rendering the potentially adhesive component adhesive and bonding the fibres to each other where they are in contiguous relationship and subsequently compacting said structure to deform the crimped composite fibres, and setting at least a proportion of the assembly in its compacted state.

The fibrous structures containing the composite fibres may be utilised in numerous ways and the structures may take various forms depending upon the particular bonded textile material desired. Thus, in the preparation of a Woven or knitted fabric the composite fibres either alone or in admixture with non-activatable fibres may be carded and then subjected to drafting and spinning to produce a yarn. The yarn after it has been woven or knitted is then treated to develop crimp and render adhesive the potentially adhesive component, the treatment serving to stabilize both the structure of the yarns within the fabric and the structure of the fabric as a whole by adhesion of fibres at points of intercrossing of the yarns. In continuous filament form the composite fibres containing a potentially adhesive component may be fabricated into cards by plying, after which the plies may be bonded together.

Besides mixing fibres of relatively short lengths such as staple fibres in the manner contemplated in the descriptions above, the yarns may be formed by continuous filaments some or all of which are composite fibres and such yarns may be formed into woven or knitted or plied structures in the same manner as a staple fibre yarn.

Utilisation of composite fibres in this manner affords textile fabrics of a knitted, woven or plied character wherein the tendency of the component yarns and filaments to slip with respect to each other is virtually eliminated but Where fabric drape and handle is not sacrificed.

Yarns consisting of or containing composite fibres may be utilised in the manufacture of laid or woven scrims which are employed, for example, for the reinforcement of sheets of plastic. The use of composite fibres in the manufacture of scrims greatly simplifies the operation since bonding can be accomplished simply by the applica tion of heat and pressure and thus the necessity for using a heat resistive warp size or dipping the structure in an adhesive before bonding on the loom is eliminated.

In a particularly useful embodiment of this invention the fibrous structures in the form of fibrous Webs are employed in the production of non-woven fabrics.

The fibres are formed into a Web of convenient thickness by a variety of methods, the method selected in a particular instance, depending to a very large extent on the length of the fibres when fibres other than continuous filaments are used.

Staple fibre webs may be prepared, for example, by a woollen or cotton carding machine or a garnetting ma chine which result in a web in which the staple fibres are oriented predominately in one direction. The thin web obtained from a single card or garnet may be used by itself but generally it is necessary and desirable to superimpose a plurality of such webs to build up the web to a sufficient thickness and uniformity for the end use intended. In building up such a web, alternate layers of carded webs may be disposed with their fibre orientation directions disposed at a certain angle, conveniently with respect to intervening layers. Such cross-laid webs have the advantage of possessing approximately the same strength in at least two directions. Furthermore cross lapping in this manner provides a product having a balanced stretchability. Random or isotropic staple fibre webs may be obtained, for example, by air-laying staple fibres. Thus, one staple fibre Web suitable for use in the process of this invention may be obtained by feeding continuous filaments to a cutter or breaker which discharges the fibres into an air stream produced by the blower. Suitable conduits are provided to guide a suspension of the staple fibres in a current of air to a foraminous surface on which the fibres settle as an interlaced and matter layer preferably being encouraged to do so by the application of suction on the other side of said surface. The foraminous surface can be in the form of an endless belt which is caused to travel past the place at which the fibres are fed to it, so as to form a continuous layer of indefinite length. Instead of having a travelling flat screen, a stationary formed screen may be used for the formation of shaped articles. For example, it may take the form of a hatshaped cone such as is used in the hatting trade. Alternatively, it may have any other form suitable for producing the desired shape of the bonded-web nonwoven products of this invention. A method of making a web containing fibres of a shorter length, say 0.5 inch or shorter, involves a wet laying technique such as use of a Fourdrinier or other paper-making machine.

Continuous filament webs of composite fibres may conveniently be prepared by drawing off directly from a spinning (i.e. polymer extrusion) unit, usually as a bundle of filaments, or they may be formed from a package or other storage device for yarn (multifilaments) or monofilament already spun. Thus the filaments (mono or multi) may be formed into a layered web by feeding them onto a collecting surface where they accumulate in overlapping layers, the individual filaments in each layer beingpredominantly coplanar, lying parallel or substantially parallel to the collecting surface and to -the bottom and top of the web so formed.

Conveniently, the step of web formation is accomplished by mechanical means, such as forwarding jets, which may be operated to lay the filaments down at random or in some desired pattern. The collecting surface may be rotated or oscillate to produce even accumulation of the filaments, a moving belt may be used as the collecting surface and in one embodiment of this invention described more fully hereinafter the continuous filament web is laid directly onto a moving belt.

A convenient method for preparing a continuous filament web in which the filaments are multifilaments is disclosed in our British Pat. No. 1,088,931.

If desired the fibrous web may be needle-punched on a conventional needle loom and/ or a light woven scrim may be incorporated therein. consequent upon formation of the fibrous web, fibres therein are crimped and bonded together.

When non-woven webs are compacted after developing the crimp in the composite fibres, compact porous leatherlike materials can be produced. The bonded material should be compacted whilst the potentially adhesive component is adhesive so that at least a proportion of the assembly can set in its compacted state and the compacting can take place whilst at least a proportion of the potentially adhesive component is initially adhesive or can take place at a later time when the component is rendered adhesive. The appearance and properties of the compacted non-woven materials depend not only on the properties of crimped fibres but also on the degree of compaction and the period which elapses between the potentially adhesive component being rendered adhesive and the compaction step. Thus the material obtained by compaction of a bonded web in which a considerable amount of the potentially adhesive component is still adhesive, for example by compacting immediately after the component is rendered adhesive, is of a different nature and appearance to that obtained by allowing an interval of time to elapse before compacting the bonded web, when the potentially adhesive component at and close to the surface of the bonded Web is no longer adhesive, although that in the centre of the web still is. The material obtained by immediate compaction is of a uniform density whilst the material obtained from delayed compaction is of variable density with a very dense centre and less dense surface layers.

Compaction of the bonded Web can be effected, for instance by pressing between rolls or plates and preferably pressures of at least 20 lbs. per square inch are utilised in order to obtain useful leatherlike materials. As an alternative to compacting the web within a short time after bonding it is possible to press the web between rolls or plates at least one of which is heated. With such heating it is possible once again to produce products having uniform or non-uniform densities and to produce products of low density in the centre and high density in the surface layers. When non-uniform density products are produced useful products can often be obtained by slitting the products at or near their centres and it is also possible to raise naps on the surface of the materials by any manner known in the art, such as buffing with emery covered rolls followed by brushing, in order to produce a suede-like effect.

Preferably the non-compacted non-wcven products of the present invention have densities in the range from 0.01 to 0.08 gms./cm. porosities of at least 75 percent and tensile strength to density ratios of at least 200 and the compacted non-woven products of the present invention have densities of at least 0.08 gm./cm. and a tensile strength of at least kg./gm./cm. The non-woven products of the present invention are useful in many diversified fields such as insulating interlinings, apparel fabrics, brassiere pads, helmet liners, hat bodies, sleeping bags, pillows, blankets, bedspreads, crash pads, surgical pads, carpet underlays, fillers, upholstery, luggage, handbags and also find use in laminates.

The invention will be more readily understood by reference to the accompanying drawings wherein:

FIG. 1 shows diagrammatically, by way of example, in perspective, an apparatus useful for making a sheet-like article according to this invention by a continuous process;

FIG. 2 shows a schematic representation of a fibrous web formed by a part of the apparatus of FIG. 1 and subsequently treated to give a sheet-like article according to this invention;

FIG. 3 is a photograph, i.e representation on an enlarged scale (x10) of a section of the sheet-like article of Example 1;

FIG. 4 is a photograph, i.e. representation on an enlarged scale (X10) of a section of the sheet-like article of Example 9;

FIG. 5 is a diagrammatic representation, in perspective, of a process for making a hat body according to this invention;

FIG. 6 is a diagrammatic representation, in perspective, of a laminated article provided by this invention; and

FIG. 7 is a cross-sectional elevation along the line VlI-VII of the laminated article of FIG. 6.

Referring now to FIG. 1 of the drawings, sheet material may be prepared by forming a fibrous web of continuous monofilaments, for example, heterofilaments, by drawing such filaments 11 off a number of bobbins (not shown) or like storage device for filaments already spun, and then forwarding the filaments between two feed rolls 12 having fluted surfaces onto a Wire mesh conveyor belt 14. The rate of deposition of the filaments onto the conveyor belt 14 is faster than the speed of the belt as a result of which the filaments are disposed in the fibrous web 13 in a random configuration without parallelism between individual filaments as is more clearly brought out in FIG. 2 described hereinafter.

The fibrous web 13 after deposition on the belt is carried through oven 15, in which the filamentary material is crimped and bonded by heating to a suitable temperature. Rolls 16 lightly grip the resultant sheet material and forward it to a collection point at 17. In an alternative apparatus for forming sheet material from fibrous webs of continuous filaments, the continuous filaments may be deposited directly onto the belt to form the web by means of jet devices.

The random dispersed arrangement of the continuous filaments making up the fibrous web 13 of FIG. 1 is illustrated diagrammatically in FIG. 2 of the accompanying drawings. The randomness of the filaments 11 of which the web is composed can be ascertained by examining square samples such as the one indicated at A. Such a sample, regardless of where in the sheet it is taken, has substantially'the same number of filaments crossing each side of the square.

The non-woven products of this invention and the process for manufacturing the same will now be more clearly illustrated in the following examples which are not to be regarded as limitative of the invention. The tensile strength of the products is determined on a 6 inch long and two inch wide strip employing an Instron Tensile Tester the jaws of which were set cms. apart. For the purposes of this invention, tensile strength is determined at room temperature under ambient conditions of 60 percent relative humidity and a rate of elongation of 5 cm./minute i.e. 100 percent.

EXAMPLE 1 This example illustrates the formation of a sheet-like article consisting of 100% composite fibres. A quantity of 12 denier, one and one half inch staple fibre formed from fully drawn potentially crimpable polyhexamethylene adipamide/poly(omega-aminoundecanoic acid) (nylon 66/ 1 1) composite fibres in which the two components are present in equal proportions by weight and in a sideby-side relationship, having a slight helical crimp caused by the drawing process, was carded using a Shirley miniature carder into a web 2.5 cm. thick, having a density of 0.005 gm./cm. This web was then heated in an oven for 3 minutes at a temperature of 230240 C. under an initial pressure of 0.04 gm./cm. provided by a 15 X 28 cm. 19 .gram weight so as to give the product a smooth surface.

Initially the fibres forming the web crimped in a helical manner and the web retracted into a smaller volume (approximately 15 percent shrinkage in area). The crimp formed in the fibres was in the opposite sense and much tighter to that in the unrelaxed fibres, and this reversal and tightening of crimp caused the fibres to squirm and become interlocked and mechanically bound together.

As the fibres attained the ambient oven temperature, by which time they were substantially fully crimped, the lower melting component of the composite fibres i.e. the poly (omega-aminoundecanoic acid) which melts at a temperature of around 165 C. became adhesive, developed its coalescent or adhesive characteristics and caused fibres in contact with one another to stick or fuse together. The resulting sheet had an average density of 0.035 gm./cm. an excellent resiliency, being deformed under compression but regaining its original form after the pressure had been removed and on the macroscopic scale had the appearance of a foam like material. The self-supporting sheet an enlarged (X10) photograph of a portion of which is shown in FIG. 3 had a textile-like handle, was exceedingly porous, quite flexible and had very good abrasion and tearing resistance.

The porous nature of the sheet can readily be appreciated by reference to FIG. 3 which shows crimped fibres 18 bonded together at points where they cross and contact one another thereby forming a three dimensionally integrated structure and, in the interstitial spaces between and among the fibres, pores 19.

The various properties of the sheet were then determined on a sample thereof and are shown in the table below:

10 In this and other tables reproduced in this specification porosity is a measure of the percentage of the overall volume of the product which is void and S/D represents the ratio of the tensile strength in g./gm./cm. to the density in gm./cm.

Density, gm./cm. 0.035 Weight per unit length, gm./cm. 0.091 Extension to break, percent 66 Tensile strength kg./gm./cm. 130 Porosity, percent 96.8 S/D 3710 Under the microscope, the polyamide fibres could be seen as joined to one another at points where they crossed over or touched by the poly(omega-aminoundecanoic acid) component which formed a minute blob at such points but which remained, along the entire length of the fibre, in contiguous association with the polyhexamethylene adipamide component. Moreover, the interstitial spaces between fibres were completely free from any bonding material, i.e. there was little evidence of any window-paning.

Since the sheet had a homogeneous structure, in the sense, that it consisted entirely of fibres all of which were selected from the same chemical classification i.e. all fibres had the same functional groups, it was readily dyed uniformly with only one dyestuff.

The sheet of this example was dyed with an acid type dyestuif for example, Solway Blue, used for polyamide dyeings to a uniform and even shade, the resulting soft resilient structure being useful as a floor-covering. The material was easily embossed to give a sharp and permanent pattern by pressing the surface with a patterned heated embossing plate.

EXAMPLE 2 A quantity of the staple fibres of Example 1 was blended with a quantity of non-activatable stufier-box crimped polyhexamethylene adipamide 1 /2 inch 6 denier per filament staple fibre in a 60/40 ratio by weight. A portion of this blend was carded using a Shirley miniature carder into a loose web 1.3 cm. thick, having an average density 0.02 gm./cm. The web was heated in an oven for 4 minutes at a temperature of 220232 C. and under an initial pressure of 0.05 gm./cm. to give the resulting product a smooth surface. As the fibres attained the ambient oven temperature, by which time the composite were substantially fully crimped the lower melting component of the heterofilament, i.e. poly(omega-aminoundecanoic acid) became adhesive, developed its coalescent or adhesive characteristics and caused fusion or sticking together of fibres of the composite (fibres which were in contact with each other or non-activatable fibres. As a result of the heat treatment the web shrank about 25 percent in area to give a sheet which had an average density of 0.03 gm./cm. and a more open structure than that obtained in the previous example using composite fibres. The open nature of the sheet which had a void content i.e. porosity of 92 percent (approximately) was demonstrated by holding the sheet up between the eye and a source of light when it was highly translucent. That is to say, objects were clearly visible therethrough indicating many unobstructed paths through the sheet thickness. In fact, when the sheet was held very close to the eye thus eliminating nearly all light registering on the eye which did not pass through the sheet it appeared to be virtually transparent. When held up to a stream of water running from a tap, the stream was distorted only slightly in passing through the sheet.

The sheet did not possess to such a marked degree the foam like appearance of the sheet consisting of 100 percent composite fibres, as fabricated in Example 1 but had a better developed textile-like softness and drape. Its soft, flexible, drapable and crease-resistant nature made it very suitable for use as a coat interliner.

Various properties of the sheet were then determined on a sample thereof. Details of the measurements and properties are listed in the table below:

Density, gm./cm. 0.025 Weight per unit length grn./ cm. 0.090 Extension to break, percent 60 Tensile strength, kg./gm./cm. 82 Porosity (approx), percent 97.8 S/D 3280 EXAMPLE 3 In this example a quantity of staple fibre composite fibres of Example 1 was blended with an equal quantity by weight of non-activatable polyhexarnethylene adipamide 1% inch 6 denier per filament staple fibre having a trilobal cross-section. The blend was carded by means of a Shirley miniature carder into a loose web, average density 0.008 gm./cm. and then heated in an oven for 3 minutes at a temperature of 220240 C. to develop crimp and activate the poly(omega-aminoundecanoic acid) component of the composite fibres. The resulting sheet had an average density of 0.02 gm./cm. a soft pleasant handle comparable with many woven articles and was dimensionally strong and flexible enough to have a good drape. The sheet dyed with an acid type dyestuif gave a soft red blanket of good tear and wearing resistance.

A 6 cm. long and 2 cm. wide sample of the sheet was found to have a density of 0.021 gm./cm. a weight per unit length of 0.071 gm./cm., an extension to break of 70 percent a tensile strength of 65 kg./gm./cm., a porosity of 98.2 percent and a tensile strength to density ratio of 3,095.

EXAMPLE 4 1A non-woven carded web as in Example 2 but composed of 20 percent by weight of the composite fibres and 80 percent by weight of the non-activatable stutr'erbox crimped polyhexarnethylene adipamide fibres was allowed to shrink freely in all directions whilst being heated in hot air at a temperature of 230 to 240 C. for a period of 3 /2 minutes at which temperature the poly- (ornega-aminoundecanoic acid) component of the composite fibres was activated i.e. developed its adhesive characteristics, thereby fusing together composite fibres in contact with one another and with the non-activatable fibres. The area shrinkage was about 12 percent and the resulting sheet had an average density of 0.020 gm./cm. Various properties of the sheet were then determined on a sample 6 cm. long and 2 cm. wide and the results are listed in the following table:

Density, gm./cm. 0.019 Weight per unit length, gm./ cm. 0.031 Extension to break, percent 18 Tensile strength, kg./gm./cm. 70 Porosity, percent 98.3 S/D 3683 The sheet had a very open structure, and was extremely flexible there being little evidence of window-paning (i.e. there was preservation of substantially all the inter stitial spaces) and could be crumpled and folded and then spread out tflat in its original state. In appearance it was very similar to a conventional woolen blanket fabric and it was bulky and light with good heat insulation properties. It dried quickly after wetting and was readily dyed uniformly with only one dyestutf. The sheet was subsequently made into a bed blanket which had excellent wearing qualities.

EXAMPLE 5 A quantity of 6 denier two and quarter inch staple fibre was formed from a fully drawn potentially crimpable polyhexarnethylene adipamide/poly(omega-aminoundecanoic acid) (nylon 66/ 11) composite fibres in which the two components were present in equal proportions by weight. The fibres were then carded on a Shirley miniature carder and then cross-lapped in a conventional manner into a loose layered web having a thickness of about 1.5 inches. This web was then divided into two 9 inch long and 6% inch wide webs each having a weight of approximately 4 ounces per square yard and an average density of 0.005 gm./cm. The webs were then placed one on each side of a light woven scrim having 5 picks per inch and 5 ends per inch. This sandwich structure was then lightly needle-punched on a single bed needle loom in order to enhance the dimensional stability and tensile strength. After needling, the structure was heated in an air over for 4 /2 minutes at a temperature of 230240 C. under an initial pressure of 0.03 gm./ cm. provided by a mica sheet so as to smooth the surface of the web. During this heating period the composite fibres crimped, the web gradually shrank, losing about 22 percent of its area and the poly(omega-aminoundecanoic acid) component of the composite fibres was activated thereby developing its coalescent or adhesive characteristics and causing fibres in contact with one another to stick or fuse together.

The resulting self-supporting sheet had a smooth uniform surface and was resistant to delamination and tear- Various properties of the sheet were then determined as in the previous examples and the results are listed in the table below:

Strength, kg./gm./cm. 220 Porosity, percent 95.2 S D 4000 Density, gm./cm'. 0.055 Weight/unit length, gm./ cm. 0.108 Extension to break, percent 29 The sheet had excellent resiliency, was uniformly p0- rous and very suitable for use as a cushioning or upholstery material.

EXAMPLE 6 A quantity of 20 denier two and a quarter inch staple fibre formed from potentially crimpable composite fibres consisting of equal proportions by weight of polyhexarnethylene adipamide and a /20 random copolymer of polyhexarnethylene adipamide and poly-epsilon-caprolactam (nylon 66//66/6) the two components being arranged in a side-by-side relationship was carded on a Shirle'y miniature carder and the laps so formed laid on top of each other with successive laps disposed at an angle of with respect to the previous lap so forming a crosslaid web having a weight of 8 ounces per square yard and a density of 0.01 gm./cm. The web was then immersed for a period of 30 seconds in 3.6 N nitric acid (21 C.) contained in a bath. This solvent treatment using nitric acid resulted in a 20 percent shrinkage of the web, crimping of the composite fibres and activation of the copolymer component which developed its coalescent or adhesive characteristics thereby causing the sticking together of fibres in contact with one another. Immediately on removal from the nitric acid bath the sheet was rinsed well with cold Water and thereafter dried.

A 6 cm. long and 2 cm. wide sample of the sheet was found to have a density of 0.038 gm./cm. a weight per unit length of 0.090 gm./cm., an extension to break of 22 percent, a tensile strength of 130 kg./gm./cm., a porosity of approximately 96.7 percent and a tensile strength to density ratio of 3,421.

EXAMPLE 7 A quantity of the staple fibre of Example 6 was carded using a Shirley miniature carder and the laps so formed cross-laid to give a web having a weight of 5 ounces per square yard and a density of 0.01 gm./cm. A portion of the cross-laid web 6 /2 inches long and 6 inches wide was immersed in a formaldehyde/ glycerol mixture at a temperature of C. for a period of 15 minutes.

During this period the fibres crimped, the web shrank by approximately 25 percent and the copolymer component of the composite fibres was activated thereby developing its adhesive characteristics and causing fibres in contact with one another to stick or fuse together to form a self-supporting sheet. Immediately after this solvent treament the web was washed with hot water and the resulting porous sheet had a uniform smooth surface, an excellent resiliency, being readily compressible, and upon release of pressure, capable of recovering substantially completely to its initial uncompressed form, and was quite flexible. It had the following properties:

Continuous filaments consisting of equal proportions by weight of polyhexamethylene adipamide and an 80/20 random copolymer of polyhexamethylene adipamide/polyepsilon caprolactam (nylon 66//66/6) were laid into a web by the method described in our British Pat. No. 1,088,931.

A portion measuring 12% inches long and 8 /2 inches wide of this continuous filament web was placed in a pressurized steam chamber. The pressure of the saturated steam was raised to 80 psi and held at this level for approximately four minutes. During this period the composite fibres crimped, the web shrank about 15 percent and the filaments in contact with each other fused together to form a stable sheet as a result of activation of the copolymer component of the composite fibres.

The strength of the sheet in the longitudinal and transverse directions was measured on samples 61 cm. long and 2 cm. wide, which are clamped between the jaws of the Instron Tensile Tester, the jaws being set cm. apart. The load and percentage extension to break are measured and the strength calculated.

Details of the measurements etc. are as follows:

Density, gm./cm. 0.024 Weight per unit length, gm./cm 0.025 Extension to break, percent 49 Strength, kg./gm./cm. 95 Porosity, percent 97.8 S/D 3,958

EXAMPLE 9 This example illustrates formation of a bonded web non-woven product in sheet form from a wet-laid web.

An uncrimped tow of fully drawn 12 denier composite fibres in which polyhexamethylene adipamide was one component and an 80/20 random copolymer of polyhexamethylene adipamide/poly-epsilon-caprolactam the other (nylon 66//66/6) was cut into 4 inch length staple in a Dorstling flock cutting machine. A ten gm. quantity of this staple was dispersed, by vigorous agitation over a ten minute period, in three litres of water containing a small quantity of Dispersol V.L. (the word Dispersol is a registered trademark). The resulting uniform suspension is filtered over an 8-inch square of 100 mesh wire screen to give a uniform coherent web in the form of a hard sheet. After drying, the sheet was placed in an air oven and heated at a temperature of 226236 C. for a period of three and a half minutes under a light pressure (0.06 gm./ cm?) provided by a mica sheet in order to smooth the surface of the resultant product. During the heating treatment, fibres of the web crimped, the web shrank, and fibres in contact with one another fused together as a result of the development of the adhesive characteristics of the copolymer component to give a stable sheet product. This sheet, an enlarged (x10) photograph of a portion of which is shown in FIG. 4 of the accompanying drawings, had an excellent resiliency and good flexibility.

The porous nature of the sheet can readily be appreciated by reference to FIG. 4 which shows crimped fibres 20 and pores 21.

The sheet had a density of 0.32 gm./cm. a weight per unit length of 0.055 gm./cm., an extension to break of 35 percent, a tensile strength of 112 kg./gm./cm., a porosity of 97.2 percent, a tensile strength to density ratio of 3,500 and a firm but flexible handle, rendering it suitable for use as a suiting interlining.

As an alternative to forming the web by a batch operation it may be prepared on a continuous basis, on a Fourdrinier or other paper-making machine.

EXAMPLE 10 A quantity of 20 denier two and a quarter inch staple fibre formed from potentially crimpable composite fibres consisting of equal proportions by weight of polyhexamethylene adipamide and an /20 random copolymer of polyhexamethylene adipamide and poly-epsilon-caprolactam (nylon 66/ 66/ 6) the two components being arranged in a side-by-side relationship was carded on a Shirley miniature carder and the laps so formed laid on top of each other with successive laps disposed at an angle of with respect to the previous lap thereby forming a cross-laid web having a weight of 7 ounces per square yard and a density of 0.01 gm./cm.

The web was then immersed in boiling water, when the fibres crimped and the resulting helically coiled fibres interlocked one with another to provide a coherent structure in which the individual fibres were so tightly bound together that they could not be removed except by breaking. During this period the web shrank approximately 15 percent in area. The crimped and shrunk web was found to have a tensile strength of several 'kg./gm./cm. Thereafter the web was heated in a hot air oven at a temperature of 230-240 C. for a period of 4 minutes. Further shrinkage took place and the copolymer component through development of its adhesive characteristics caused bonding of the fibres where they cross-over or contacted one another.

The resulting sheet-like article had a feel very similar in certain respects to sponge or a foam rubber but differ ent therefrom in having a uniform elasticity and strength in all directions in the plane of the sheet. It had the appearance of a closely matted mass of fine fibres distributed more or less randomly throughout the structure with the fibres bonded together at cross-over and contact points. The product was also distinguishable from a foam rubber in that it was air and liquid permeable and had a higher tear strength.

The sheet dyed uniformly with an acid type dyestufl. and was found to be very useful as a cushioning material.

Various properties of the sheet were then determined on a sample 6 cm. long and 2 cm. wide and the results are listed in the following table:

Density, gm./cm. 0.035 Weight per unit length, gm./ cm. 0.099 Extension to break, percent 118 Tensile strength, kg./gm./cm. 55 Porosity, percent 96.9 S/D 1,571

EXAMPLE 11 The bonded web non-woven product of this invention may be in the form of hat body. For example, there is shown in FIG. 5 of the accompanying drawings, one embodiment of a process of making such a hat body.

A quantity of the staple fibres of Example 1 is corded using a Shirley miniature carder and cross-lapped in a conventional manner into a strip of a loose layered web having a thickness of about 1 inch and a density of about 0.005 gm./cm. The strip 22 is wound in overlapping 15 relation on a hat mould 23 which is mounted upon a base 24 and rotated by means of a shaft 25. By rotating the mould 23, the strip may be applied to surface of the mould in overlapping layers, as illustrated, until a layer of requisite thickness is built up. At this point, the hat mould is placed in an air oven at a temperature of 220 240 C. for a period of about three minutes. During this period, fibres of the web crimp, the web shrinks so that the over lapping sheets more faithfully reproduce the shape of the hat mould and a coherent structure results from the fusion or sticking together of fibres which contact one another. If the thickness of the strips 22 is not too great, it is possible that during this heating treatment, the lines defining the overlapping areas will substantially disappear so that no surface finishing of the hat body will be necessary.

In an alternative embodiment, the web from. which the hat body is prepared may be made by air deposition of the staple fibres on a stationary formed screen in the form of a hat-shaped cone. Suction may be applied beneath the screen to assist deposition of the fibres thereon. Fibres of the web may subsequently be crimped and activated to form a hat body.

It will be understood that the non-woven products of this invention may be in the form of shaped articles other than hat bodies. These may be produced, for example, by shaping a sheet immediately after fibres of the web are bonded together and before the sheet has cooled into the required shape, which shape they retain on cooling. For example, short sections of pipe may be covered with a layer of insulating material by wrapping the hot sheet about the pipe until a layer of requisite thickness has been built up, and then allowing the structure to cool. Such wrapping can be effected without extensive rupture of the bonds between the fibres and without excessive compacting of the sheet, which thereby largely retains its bulky characteristics with numerous small air spaces and high insulating value.

This insulation is in the form of a continuous sleeve free from longitudinal seams or cracks.

Shaped articles may also be formed by a process which involves filling or lining a mould member with a fibrous web and then crimping and activating fibres of the Web so that the web sets in the shape of the mould.

In consequence of the crimping the filamentous mate rial is present in the finished product in a convoluted, nonlinear disposition which provides flexibility, bulk and resilience.

The.following two examples illustrate this latter method of producing shaped articles.

EXAMPLE 12 4.3 gms. of 12 denier, two and a quarter inch staple fibre formed from fully drawn potentially crimpable polyhexamethylene adipamide/poly (omega-aminoundecanoic acid) (nylon 66/ 11) composite fibres in which. the two components were present in a side-by-side relationship, and not relaxed but having a slight helical crimp caused by the drawing process were carded using a Shirley miniature carder into a web having a density of 0.005 gm./cm. A 6-inch long test tube having a diameter of 1 inch was then filled with the fibrous web. The tube and its contents were then placed for a period of 12 minutes in an upright position in an air oven at a temperature of 232-240 C. At the end of this period the staple fibres had crimped and fused together. After cooling, the fibrous mass was broken away from the inner surface of the testtube and thereafter removed from the tube as a strong, coherent and porous shaped article which had assumed the shape of the test-tube described above. The more or less candle shaped article with a void content of over 90 percent was found to be useful, on account of its porous nature in the filtration art.

1 6 EXAMPLE 13 A female mould in the form of a spherical section 8 inches in diameter and with a greatest depth of 4 inches, the inner surface of which was heated to 150 C. and sprayed with a silicone release agent, was lined to a depth of two inches with a Web consisting of staple fibres of Example 1. A male mould member of smaller dimensions was placed in the female mould so that the fibrous web occupied the annular space between the two mould members and the composite mould was thereafter inserted in an air oven where it was maintained at a temperature of 220-230 C. for a period of 10 minutes.

The result of this moulding treatment was a lightweight, soft and flexible cup-shaped article which had the dimension of the spherical section described above. The article had permanence of form, washability, durability, strength, reasonable softness and flexibility and permeability to air and moisture so as to breathe properly. Tapes, fasteners and the like can be sewn directly onto the edges of the cup which is useful where a strong resilient structure is required, such as, in brassiere pads and helmet liners.

EXAMPLE 14 The bonded web non-woven products of this invention have numerous applications in the laminating art either as interlayers or backing sheets in conjunction with plastic films and sheets such, for example, as of nylon or polyethylene or in conjunction with textile fabrics of woven, braided, knitted, knotted or felted character.

For example, referring to FIGS. 6 and 7, the selfsupporting sheet 26 as prepared in Example 1 was disposed between layers of fabric 27 the inner surfaces of each layer of which were coated with rubber latex adhesive which served to unite the fabric layers to the sheet 26. The laminated structure so produced is particularly useful for upholstery and cushioning purposes since it possesses an excellent resiliency on account of the properties of sheet 26 and with an appropriate fabric 27 can have a pleasant, warm handle.

EXAMPLE 15 A quantity of 12 denier, two and a quarter inch staple fibre formed from a fully drawn potentially crimpable polyhexamethylene adipamide/poly( omega-aminoundecanoic acid (nylon 66/11) composite fibres in which the two components are present in equal proportions by weight and in a side-by-side relationship, having a slight helical crimp caused by the drawing process, was carded using a carder into a Web 2.5 cm. thick, having a density of 0.01 gm./cm. This web was then heated in an air oven at a temperature of 230235 C. for three minutes during which period fibres of the web crimped, the web shrank approximately 15 percent in area and the lower melting point component of the composite fibres i.e. the poly- (omega-aminoundecanoic acid) became adhesive, developed its adhesive characteristics and caused fibres in contact with one another to stick or fuse together.

At this stage the bonded Web weighed about 5.2 ounces per square yard and was about 1.5 inches thick.

Within 5 seconds after its removal from the air oven the bonded web was compacted between two flat plates unclller a pressure of approximately pounds per square 1nc The resulting material in sheet form was uniformly porous and had an appearance and feel similar to that of natural leather. The material had the following physical properties.

Density, gm./cm. 0.15 Weight per unit length, gm./ cm. 0.038

Extension to break, percent 16 Tensile strength, kg./gm./cm. 248 Porosity, cc./sec./cm. 24

The air permeability value is a measure of the porosity of the material and it represents the rate of flow of air, in centimeters per second, through 1 sq. cm. of fabric 1 cm. thick necessary to produce a pressure drop of 1 cm. Of H20.

Under the microscope it could be observed that the structure contained myriads of intercommunicating pores in the interstices between and among fibres of the web and the fibres could be seen as joined to poly(omegaaminoundecanoic acid) component which formed a minute blob at such points, but which remained, along the entire length of the crimped fibre, in contiguous association with the polyhexamethylene component. The deformation of the crimped composite filaments took a variety of forms which was a reflection of the variety of crimp shapes present in the bonded web prior to compaction. The shapes range from a fully developed spirally coiled crimped composite filament to one in which there is merely a crinkle or bend. The former on compaction, may, in appropriate circumstance, behave somewhat like a coil spring while the latter may cr'umple upon itself with the ends of the filament moving in toward one another.

The material of this example was a strong, breathable sheet suitable for a surface covering or a leather replacement.

EXAMPLE 16 40 gms. of 12 denier per filament two inch staple fibres formed from a fully drawn potentially crimpable polyhexamethylene adipamide/poly epsilon caprolactam (nylon 66/6) in which the two components were present in equal proportions by weight and in a side-by-side relationship, were carded into a Web 3 cm. thick, having a basic weight of 4 ounces per square yard. A portion of this web was then heated in an air oven at a temperature of 230235 C. for a period of 3 minutes under an initial pressure of 0.2 gm./cm. provided by an aluminium sheet. The application of this light pressure during heating provided the resulting product with a smooth surface, when it would otherwise be somewhat rough and fuzzy. During the heating period, the composite fibres crimped and fused together at points where they crossed-over and contacted one another following activation of the poly-epsilon-caprolactam component of the composite fibres. There was an overall shrinkage in the area of the web of about 18 percent, and the product comprised a bonded fibre web having a relatively open and bulky structure with a low density.

Within 6 seconds after its removal from the air oven i.e. while substantially all the potentially adhesive component was still in a tacky condition, the bonded web was compacted between two calender rolls which exerted a pressure of approximately 120 pounds per square inch on the bonded web.

The compacted material in sheet form had an appearance and feel similar to that of natural leather. A variety of properties of the sheet were then determined on a sample thereof and the results are tabulated below:

Density, gm./cm. 0.28 Weight per unit length, gm./cm. 0.052

Extension to break, percent 21 Tensile strength, kg./gm./cm. 315 Porosity, cc./sec./cm. 12

The sheet which contained deformed crimped fibres, which could be seen when a portion of the sheet was examined under a microscope, had a useful flexibility and did not crack on repeated bending. The surface of the material could be raised and the material given the general appearance and feel of suede leather by passing the compacted sheet through a sueding calender, in which the surface of the sheet come in contact with a roller coated with emery powder and revolving at 1500 revolutions per minute.

The material itself was a useful leather-replacement but we find that for some application it was advantageous to apply to one or both surfaces of the sheet a suitable coat. We prefer that the coat has a thickness of between 2 to 4 mils. Polyurethanes make excellent coating materials and the composite structures so formed are particularly useful in the upholstery art.

EXAMPLE 17 A quantity of the staple fibres of Example 15 was blended with a quantity of non-activatable stulfer-box crimped polyhexamethylene adipamide 1 /2 inch 6 denier per filament staple fibre in a 60/40 ratio by Weight. A portion of this blend was carded using a Shirley miniature carder into a loose Web 1.3 cm. thick, having an average density 0.02 gm./cm. The web was heated in an oven for 4 minutes at a temperature of 220-232 C. and under an initial pressure of 0.05 gm./cm. to give the resulting product a smooth surface. As the fibres attained the ambient oven temperature, by which time the composite fibres were substantially fully crimped the lower melting component of the composite fibres i.e. poly(omegaaminoundecanoic acid) became adhesive, developed its coalescent or adhesive characteristics and caused fusion or sticking together of composite fibres which were in contact with each other or non-activatable fibres. As a result of the heat treatment the web shrank about 25 percent in area to give a bulky porous sheet which had an average density of 0.03 gm./'cm.

The bonded web within seconds of its removal from the air oven was pressed between a flat metal plate and a rubber pad for a period of about 1 to 2 minutes, to produce a compact, porous structure containing deformed crimped fibres. The resulting sheet had a leather-like appearance and general feel, but it was in addition more soft and supple and the smooth surface had better crease resisting qualities than the material made according to Example 15.

A number of properties of the sheet which were determined on a sample thereof are listed in the following table:

Density, gm./cm. 0.19 Weight per unit length, gm./cm 0.036

Extension to break, percent l6 Tensile strength, kg./gm./cm. 195 Porosity 20 EXAMPLE 1 A quantity of 12 denier per filament two and a quarter inch staple fibres formed from potentially crimpable composite fibres consisting of equal proportions by weight of polyhexamethylene adipamide and an /20 random copolymer of polyhexamethylene adipamide and polyepsilon-caprolactam (nylon 66/ 66/ 6) the two components being arranged in a side-by-side relationship was carded on a Shirley miniature carder and the laps so formed laid on top of one another with successive laps disposed at an angle of with respect to the previous lap so forming a cross-laid web having a weight of 8 ounces per square yard and a density of of 0.01 gm./cm.

The dimensional stability of the web was improved by lightly needle-punched on a conventional single bed needle loom (nominal penetration of inch and a rate of needling of punches per square inch). Thereafter, the web was heated in an air oven under an initial pressure of 0.15 gm./cm. provided by a mica sheet 230-240 C. for a period of 3 /2 minutes. The result of this heat treat ment was to crimp the fibres, shrink the web (approximately 20 percent) and cause fusion of the fibres at points where they cross-over or meet one another. Immediately after its removal from the air oven the bonded web was pressed between two flat chip boards the applied pressure being approximately 85 pounds per square inch; in consequence of the application of compaction pressure in this manner, crimped fibres of the bonded web were deformed and a compact, porous sheet structure produced. The sheet had a density of 0.24 gm./cm. a weight per unit length of 0.043 gm./cm., an extension to break of 9 percent, a tensile strength in kg./gm./cm. of 184 and a porosity of 14 cc./sec./ cm.

The pressed sheet may be treated by any of the processes employed to treat and finish leather and may be formed into useful leather-like products. The sheet may, if necessary, be moulded into a required shape.

EXAMPLE vl9 A non-woven carded web as in Example 17 but composed of 20 percent by weight of the composite fibres and 80 percent by weight of the non-activatable stulfer-box crimped polyhexarnethylene adipamide fibres (3 denier per filament) was allowed to shrink freely in all directions whilst being heated in hot air at a temperature of 240 to 255 C. for a period of 4 /2 minutes at which temperature the poly (omega-aminoundecanoic acid) component of the heterofilament was activated i.e. developed its adhesive characteristics, thereby fusing together composite fibres in contact with one another and with the non-activatable fibres. The area shrinkage was about 12 percent and the resulting sheet had an average density of 0.020 gm./cm. The sheet had a very open structure, and was extremely flexible there being little evidence of windowpaning (i.e. there was preservation of substantially all the interstitial spaces) and could be crumpled and folded and then spread out flat in its original state.

Immediately following its removal from the air oven i.e. while substantially all the potentially adhesive component is in a tacky condition the bonded web is compacted between 2 smooth cast iron plates which exert a pressure of 125 pounds per square inch on the fibrous web. The effect of this applied pressure is to deform the crimped fibres and provide a compact sheet structure con taining myriads of interstitial spaces which form a labyrinth of intercommunicating pores throughout the structure.

Although the sheet had the appearance of leather the ressemblance was not so well developed as in the materials of previous examples which contained more composite fibres. On the other hand, the material had a soft, pleasant handle and was extremely flexible with good crease resistance properties. The sheet possessed the following physical properties:

Density, gm./cm. 0.14 Weight per unit length, gm./ cm 0.227

Extension to break, percent 20 Tensile strength, kg./ gm./ cm 108 Porosity, cc./sec./cm. 18

Since the sheet had a homogeneous structure, in the sense, that it consisted entirely of fibres all of which were selected from the same chemical classification i.e. all fibres had the same functional groups, it was readily dyed uniformly with only one dyestuff.

The sheet of this example could be dyed with an acid type dyestutf used for polyamide dyeings to a uniform and even shade, the resulting flexible structure with a useful ability to breathe being useful for upholstery purposes. The material was easily embossed to give a sharp and permanent pattern by pressing the surface with a patterned heating embossing plate.

EXAMPLE 20 Continuous filaments consisting of equal proportions by weight of polyhexamethylene adipamide and an 80/20 random copolymer of polyhexamethylene adipamide/ poly/epsilon caprolactam (nylon 66/ 66/ 6) were laid into a web by the method described in our British Patent No. 1,088,431.

A portion measuring 12% inches long and 8- /2 inches wide of this continuous filament web was placed in an air oven and heated to a temperature of 230240 C. for a period of approximately four minutes, under an initial pressure provided by a mica sheet weighing 12 gms. During this period the heterofilaments crimped, the web shrank about 15 percent and filaments in contact with each other fused together to form a stable self-supporting sheet as a result :of activation of the copolymer component of the heterofilaments.

The bonded web was then compacted between two flat blocks of wood exerting a pressure approximately 150 pounds per square inch on the bonded web. The pressure was maintained for about 3 minutes.

The final sheet was 0.5 inch thick, and had an extension to break of 46 percent, a tensile strength .of 255 kg./ gm./cm. and a porosity of 26 cc./sec./cm. The sheet had a leather-like appearance and could be employed in making luggage and brief cases which have a useful scuff resistance, a good stitch tear resistance and the appearance of leather.

Embossed surfaces could be obtained by substituting embossed plates for the smooth wooden blocks.

The compacted sheet structure may be treated by any of the usual processes employed to treat and finish leather.

EXAMPLE 21 A quantity of 15 denier filament two and a quarter inch staple fibre formed from potentially crimpa'ble composite fibres consisting of equal proportions by weight of polyhexamethylene adipamide and an /20 random copolyof polyhexamethylene adipamide and poly-epsilon-caprolactam (nylon 66// 66/ 6) the two components being arranged in a side-by-side relationship was carded on a Shirley miniature carder and the laps so formed laid on top of each other with successive laps disposed at an angle of with respect to the previous lap so forming a cross-laid web having a weight of 8 ounces per square yard and a. density of 0.01 gm./cm. The web was then immersed for a period of 30 seconds in 3.8 N nitric acid (21 C.) contained in a bath. This solvent treatment using nitric acid resulted in a 20 percent shrinkage of the web, crimping of composite fibres and activation of the copolymer component which developed its coalescent or adhesive characteristics thereby causing the sticking together of fibres in contact with one another. Immediately on removal from the nitric acid bath the densified and shrunken web which had a density of 0.038 gm./cm. was passed between pressure rolls, of which the bottom one was driven and the top roll was free running and weighted to exert a pressure of about pounds per square inch on the material. After pressing, the compacted structure containing deformed crimped heterofilaments, was washed with water until substantially all the nitric acid was removed. The sheet had the following properties:

Density, gm./cm. 0.4 Weight per unit length, gm./cm 0.075 Extension, percent 63 Tensile strength, kg./gm./cm. 352

The material which had the appearance and feel of natural leather remained reasonably supple, crease resistant and permeable to water vapour during extended use.

Pigmented and plasticised polyvinyl chloride compositions could be applied as surface coatings to the above described sheet material to produce a good quality upholstery material.

Instead of pressing the bonded-web immediately after its removal from the nitric acid, the web, after the nitric acid treatment, may be washed with hot water to remove the nitric acid and thereafter allowed to stand for several minutes at room temperature. At the end of this period substantially all the potentially adhesive component was no longer in a tacky condition. We found that a leatherlike material could be obtained from the cold, bonded-web by hot-pressing it for three minutes at a temperature of -150 C. and a pressure of about 200 pounds per square inch. Under these conditions of heating and pressing the potentially adhesive component, at least that which 21 lies at or near to the surface of the sheet, is reactivated and this re-activation enables the crimped filaments to be deformed under the compacting pressure.

EXAMPLE 22 This example illustrates the formation of shaped articles consisting of the leather-like materials of this invention.

A quantity of the staple fibre used in Example 15 was carded using a Shirley miniature carder and the laps so formed cross-laid in a conventional manner into a strip of a loose layered web having a thickness of about 2 inches and a basic weight of 5 ounces per square yard. The web was then heated in an air oven for a period of 3 minutes at a temperature of 220240 C.

The web, immediately after removal from the oven and while the potentially adhesive component, which forms the bonds, is still in a tacky condition, was moulded under compacting pressure in a concave cast iron mould (diameter, 8 inches and greatest depth 4 inches).

The result of the moulding treatment was a flexible article with a leather-like appearance which had the dimensions of the concave mould described above. The article was suitable for use as a novelty hat.

In an alternative method, a hat-shaped article may be produced by compacting a bonded-web formed on a hat mould. The bonded-web was formed in the mould by crimping and activating a fibrous web air-deposited there- EXAMPLE 23 A quantity of the staple fibres used in Example was carded using a Shirley miniature carder and the laps so formed cross-laid to provide a layered web having a basic weight of 8 ounces per square yard. A portion of this web was heated in an air-oven for a period of 3 /2 minutes at a temperature of 230-240 C., under an initial pressure of 0.16 gm./cm. provided by a mica sheet.

The bonded-web which resulted from this treatment was removed from the oven allowed to stand at room temperature for thirty seconds. Thereafter, the bonded-web was compacted between two flat plates which exerted a pressure of about 130 pounds per square inch on the web. The effect of allowing an interval of thirty seconds to elapse between the termination of the bonding treatment and the compaction stage was to produce a material which had a very dense and compact central portion and relatively less dense surfaces. The sheet had, as a result, a heterogeneous structure. This effect finds an explanation in the fact that, as a result of the delay prior to compaction, the potentially adhesive component at and close to the surface of the bonded-web was no longer tacky.

The sheet had a basic weight of 14 ounces per square yard, an extension to break of 54 percent and a tensile strength of 222 kg./ gm./ cm.

The sheet was split down the middle to give two flexible, permeable thin sheets having the appearance of natural leather.

What we claim is:

1. A bonded fibrous material comprising at least five percent, based on the Weight of fibres in the material, of crimped composite fibres comprising at least two fibreforming synthetic polymeric components arranged in distinct zones across the cross-section of each fibre, each component being continuous along the length of each fibre and at least one, but less than all, of the components being potentially adhesive and located so as to form at least a portion of the peripheral surface of each fibre, said crimp being derived from difierent physical properties of the components, the fibres of the material being entangled with each other due to said crimp and being bonded to each other where they are in contiguous relationship by the adhesive characteristics of said potentially adhesive component whereby the material is strengthened and stabilised.

2. A bonded fibrous material as claimed in claim 1 which comprises a non-woven product having a density 22 in the range from 0.01 to 0.08 gm./cm. a porosity of at least percent and a tensile strength to density ratio of at least 200.

3. A bonded fibrous material as claimed in claim 1 which comprises a leather-like non-woven product having a density greater than 0.08 gm./crn. and a tensile strength of at least 60 kg./gm./cm.

4. A bonded fibrous material as claimed in claim 1 wherein the composite fibres comprise two fibre-forming components which are arranged side-by-side.

5. A bonded fibrous material as claimed in claim 1 wherein the composite fibres comprise two fibre-forming components and the potentially adhesive component of the composite fibres completely and eccentrically surrounds the other component.

6. A bonded fibrous material as claimed in claim 1 wherein the composite fibres comprise two components of different polyamides.

7. A bonded fibrous material as claimed in claim 1 wherein the potentially adhesive components is poly- (omega-aminoundecanoic acid).

8. A bonded fibrous material as claimed in claim 1 wherein the potentially adhesive component is a copolymer containing hexamethylene adipamide and epsilon caprolactam.

9. A bonded fibrous material as claimed in claim 1 wherein the potentially adhesive component is poly- (epsilon caprolactam).

10. A bonded fibrous material as claimed in claim 9 wherein the other component of the composite fibers is poly(hexamethylene adipamide).

11. A bonded fibrous material as claimed in claim 1 wherein the components of the composite fibers are dif ferent polyesters.

12. A process for making bonded fiberous materials which comprises forming a fibrous structure containing at least five percent, based on the weight of fibres in the assembly, of composite fibers comprising at least two fibreforming synthetic polymeric components arranged in distinct zones across the cross-section of each fibre, each component being continuous along the length of each fibre and at least one, but less than all, of the components being potentially adhesive and located so as to form at least a proportion of the peripheral surface of each fibre, said composite fibres possessing latent crimp due to different physical properties of the components, developing crimp in said fibres in the absence of any appreciable pressure to entangle them with each other, rendering the potentially adhesive component adhesive and bonding the fibres to each other where they are in contiguous relationship by the adhesive chaarcteristics of said component.

13. A process for making bonded fibrous materials as claimed in claim 12 wherein the crimped, bonded structure is subsequently compacted to deform the crimped composite fibres and at least a proportion of the assem bly is set in its compacted state.

14. A process as claimed in claim 12 in which the fibrous assembly is needle-punched.

15. A process as claimed in claim 12 in which crimp is developed and the potentially adhesive component is rendered adhesive in the same treatment.

16. A process as claimed in claim 12 which crimp is developed and the potentially adhesive component is rendered adhesive by heat treatment.

17. A process as claimed in claim 12 in which crimp is developed and the potentially adhesive component is rendered adhesive by chemical treatment.

18. A process as claimed in claim 17 in which the chemical treatment comprises contacting the fibrous structure with a non-aqueous solution of formaldehyde.

19. A process as claimed in claim 17 in which the chemical treatment comprises contacting the fibrous structure with a nitric acid solution.

20. A process as claimed in claim 13 in which the fibrous structure is compacted whilst substantially all of the potentially adhesive component is in an adhesive con- 2,774,128 12/1956 Secrist 161-150X dition. 2,994,617 8/1961 Proctor 117-4 21. A process as claimed in claim 13 in which the 2,715,588 8/ 1955 Graham et a1 117--65 fibrous structure is compacted whilst only the potentially 2,130,948 9/1938 Carothers 1854 adhesive component in the centre of the structure is in an 5 adhesive condition. OTHER REFERENCES 22. A process as claimed in claim 13 in 'which the FloYdPolYamideResins,1961,}, 18L

fibrous structure is compacted whilst only the potentially adhesive component at or close to the outer surfaces of WILLIAM J VAN B ALE/N Primary Examiner the structure is in an adhesive condition. 10

MARK A. LITMAN, Assistant Examiner References Cited 7 UNITED STATES PATENTS U.S. CL. X.R.

3,038,235 6/1962 Zimmerman 161-172X 156-148, 305, 306; 161- 154, 155, 156, 157, 170, 175 2,774,129 12/1956 Secrist 161-150X 

